Apparatus for drying paper



Feb. 27, 1934. F. c. LADD 1,949,125

APPARATUS FOR DRYING PAPER Filed April 4, 1931 2 Sheets-Sheet 1 IN VENTOR.

@0112 M TORNEYS.

Feb. 27, 1934 F. c. LADD 1,949,125

' APPARATUS FOR DRYING PAPER I Filed April 4, 1931' 2 Sheets-Sheet 2INVENTOR. FRANK L. L400 A TTORNEYS.

Patented Feb. 27, 1934 APPARATUS FOR DRYING PAPER Frank C. Ladd, TurnersFalls, Mass.

Application April 4, 1931. Serial No. 527,704

7 Claims.

' This invention relates to paper manufacture and particularly to thedrying of the paper as a final manufacturing operation. The invention isan improvement on the loft drying method in paper manufacture andincludes an apparatus for carrying on the new method.

It has long been recognized that the old and expensive loft dryingmethod in paper manufacture has definite advantages. The method resultsin a better quality of paper than where faster and less expensivemethods are used. I believe that the reason can be found in the factthat, when loft dried, the paper fibers are permitted to shrink slowlyand are free to set them-' selves in the sheet without the strain due toquick shrinkage in the rapid drying methods which are carried on athigher temperatures than in loft drying.

As commonly carried on, loft drying consists in hanging a number ofsheets on a pole and hanging a great many of these poles in a dryingroom (the loft) for slow drying. Some of the disadvantages in themethod, aside from the expense of handling the paper and poles, are thatthe poles leave pole marks and the paper is somewhat distorted byirregular hanging in sheets as the fibers are shrinking and setting totheir final form and relation.

According to my invention, I avoid much of the expense and all thedisadvantages of the irregular hanging of the paper while drying, and Iretain all the advantages of the loft drying method. Among theadvantages in both the loft drying and in my method I desire toemphasize the idea of slow drying at a low enough temperature to givethe paper the best quality. The advantages of my method over the oldloft drying method are in the Way I support the paper to keep it freefrom distorting strains while drying and in handling it through thedrying method to save expense. There are other detailed advantages inthe method and apparatus which will appear in the following descriptionand claims.

Referring to the drawings,

Fig. l is a diagrammatic view indicating two spaced horizontal conveyersfor a paper sheet and the path of an endless chain conveyer apparatuswhich carries the sheet also indicated through the space between thehorizontal conveyers and so that the sheet first turns to a verticalhanging position and then back to the horizontal position between thespaced conveyers;

Fig. 2 is a diagrammatic side view of the spaced conveyers and papertravel as shown in Fig. 1, also indicating a fall board and a riserboard adjacent the spaced conveyers to support the paper sheet as itturns from and to vertical position;

Fig. 3 is a diagrammatic view of the two end portions of the dryingapparatus arranged in line but not indicating the middle portion orendless chain conveyer for carrying the sheet between the end portions;

Fig. 4 is a vertical sectional view of one of the grippers, mounted onone of the endless conveyer chain links with the gripper guides andsupports in position to permit open position for the gripper. Thissection is taken through a gripper, for example, when it is followingthe paper sheet supported on the conveyer belt ready to take hold of theedge or after it has released the edge of the sheet, as for example atposition 4-4 or 4'4 of Fig. 1;

Figs. 5 and 6 are views like Fig. 4 but with the position of thegrippers respectively on lines 5-5 and 6-6 (Fig. 1) of their chaintravel but with the grippers closed;

Fig. 7 is a plan view of a chain section indieating one type that willpermit the twisting of the grippers carried thereby in the chainconveyer apparatus from horizontal to vertical position and back again;

Fig. 8 is a diagrammatic view with parts removed, indicating spacedportions of the gripper guides (viewed from below, see Fig. 6) arrangedalong the travel of the conveyer chain so as to permit the grippers asindicated to successively release the paper and relieve the strain ofthe sheet between grippers due to shrinkage in drying; and

Fig. 9 is a diagrammatic view of a modified way of turning the papersheet between the end portions of a drying apparatus such as shown inFig. 3.

With the apparatus shown, or by hand, I can carry on my method asfollows: I first feed a continuous sheet of paper 1, with the plane ofthe paper in a horizontal position, back and forth through a series ofbelt conveyers 2 which support the sheet. This preliminary drying isdone in a room suitable for drying, such as a loft drying room. Thepaper starts in that damp condition, just as if it were to be cut insheets, hung on poles, and loft dried. It is a fact that by feeding thecontinuous sheet 1 over the belt conveyers 2 first, I can get apreliminary drying without elevating the temperature to such a de-' greethat a large part of the total shrinkage (due to drying) isaccomplished. This shrinkage can be easily compensated for by runningprogres-- sive conveyers of the series 2 at less and less speed. Theamount of shrinkage for, say fifty feet of conveyer travel would beseveral linear inches. All that the conveyers 2 need do is to supportthe paper as it is fed to the beginning. of the series and carry itforward to the end or transfer conveyer 3 in unwrinkled condition withthe speeds of the several conveyers 2 arranged to compensate for therather large shrinkage in such travel. The preliminary drying conveyers2 arrange the paper sheet 1 in partially dried condition so that it maybe thus delivered to a transfer conveyer 3 and gripped along one edgealong the travel of conveyer 3, and the sheet turned when it is sogripped so that it hangs vertically.

I prefer to give the paper sheet a preliminary drying on the conveyermeans that supports it in horizontal position. But my method is broadenough in some aspects to dispense with such preliminary step. Forexample, with or without the preliminary drying I have conceived thestep of gripping a strip of paper adjacent one edge at spaced points,letting the paper strip hang vertically and unwrinkled as it travelsthrough. the drying room and is dried and winding up after it is dried,all in a continuous operation, with a sheet of indefinite length or acontinuously fed sheet. The paper will shrink as it is dried and whileit is hanging vertically. Such shrinkage will cause a strain along theline of the carrying edge between the carrying points that are gripped.To relieve this strain I conceived the step of successively andmomentarily releasing the points where the sheet is gripped, and takinga new grip at a point slightly offset from the point where the sheet waspreviously gripped. This plan of releasing the hanging sheet whiledrying is a special feature added to my method in its broadest aspect.

To illustrate, assume that a workman started with the forward end of adamp paper sheet as it unwound from a roll at one end of a drying room,walked toward the other end and held the edge by hand at two positions.Close behind the first workman another takes a hold of the sheet at theedge, and so on. The sheet could be thus carried through the drying roomby a single file of workmen carrying the sheet so that it hangsvertically and unwrinkled. If they all walked at a uniform speed andheld their original grips on the paper there would be no provision forshrinkage. To provide for shrinkage I conceived the idea of the gripsbeing successively released and new grips taken so the paper sheet canadjust itself, the shrinking strains can be relieved and still the gripscan be applied and carried forwardly to carry the paper all through thedrying path.

Paper that is advantageously loft dried is ordinarily of a kind thatwill take marks from what it rests on while being dried. I conceived theidea that while the paper is taking its permanent drying set conditionit is best to have it hanging vertically where both sides are exposed tothe same drying conditions and with its edges held by grips that can betemporarily released to release the shrinkage strains. The paper israther heavy and its vertically hung position for drying gives it anadvantageous dried condition. But probably one of the most importantfeatures of my method is in the idea of drying steps that lendthemselves to handling the paper efiiciently from damp to dry conditionin a continuous sheet heretofore proposed for handling continuous websof paper in the drying operation I have found that the paper does notdry out with as good quality as the old loft dried method (hanging inthe loft on sticks) will give the same paper.

T- My method and apparatus are conceived for the purpose of duplicatingall the good conditions of loft drying (by actually drying slowly underthe same drying conditions and avoiding high temperatures) and yethandling the paper to avoid loft marks and save expense.

From the foregoing description concerning the method, one can see thatthe steps in the method could be carried out by hand if workmen walked acontinuous strip of paper to be dried through the loft from a damp rollas it was unwound to a dried roll where it was wound up. To give thedesired loft dying conditions we only need to have the workmen takeenough time and operate in a loft drying room so that the paper will begiven the same slow drying exposure in such a room as would accomplishdrying. Of course the apparatus shown in the accompanying drawings isdesigned to carry out the method more efiiciently than the workmen coulddo. With this method in mind the reasons for the apparatus and some ofits detailed structure will be better understood.

Referring to the skeleton views in Figs. 1, 2, 3.

and 8, one skilled in the art will readily understand the generalstructural'arrangement as follows. mill width, is unwound as sheet 1. Iprefer to drive the roll a by any of the known means, so that it willdeliver the sheet 1 at a uniform rate to the lower belt of the series 2.At the end of such belt the sheet 1 is turned up to travel backwardlywhile supported on the belt conveyer next above. In this manner thesheet travels back and forth through the series of belt conveyers 2.These belts in the series 2 are driven at different speeds so that asthe sheet 1 shrinks the shrinkage is compensated for by a slightlyslower speed of each successive belt in the series. It is onlysufficient to arrange the conveyer driving mechanism so that theshrinkage (which is considerable) will not tighten up the sheet aroundthe belt pulleys but permit a loose travel of the sheet in horizontalfestooned manner as indicated. During this travel it will be appreciatedthat the drying sheet is laid out horizontally and fiat, supported firston-one side and then on the other as the sheet advances, which makes agood preliminary drying condition.

At the end of the upper belt in the series, the sheet is caused to passto the transfer belt 3.

The latter belt has one edge offset inwardly so that it is narroweralong one edge than the sheet of paper. Thus the paper while supportedfor its whole width on the belts 2, is supported less than its wholewidth on conveyer 3. Along one edge of belt 3 the paper overlaps andextends out in a free margin.

Atthis free margin the grippers (Fig. 4) are fed into position to takehold of the sheet. The chain 10, the guide tracks 14 and 15, the camtracks 12 and 13 (shown in Figs. 4, 5, 6) are arranged in the travelpath indicated in Fig. 1. Suitable guide and driving pulleys move thechain 10. Pairs of gripper fingers 5 and 6 are pivoted to some of thechain links so that an endless series of spaced gripper devices arecarried by the chain. f

A spring 11 tends to hold the fingers 5 and 6 apart. But at suitableparts of the chain path the cam paths 12 and 13 hold said fingerstogether to grip the paper sheet 1. The chain 10 is made so that it cantwist as well as bend. Tracks 14 and 15 are engaged by pins 18 (Fig. 4)to guide the chain and cause the chain blocks with gripper fingers 5 and6 to twist from horizontal to vertical positions and back again atappropriate parts of the chain travel. For exam- The roll a of damppaper, of any usual 100 of the sheet long enough and slow enough, .for

ple, the tracks 14 and 15 supported by hangers 16 and 1'7 (from theceiling or any suitable frame) are in position in Fig. 4 for thegrippers to close on the sheet 1 at the free margin of the paper alongconveyer 3. This is the position on line 44 of Fig. 1.

From this position to position of line 5-5 in Fig. 1 the tracks 14 and15 are gradually twisted to their position shown in Fig. 5. From suchposition at line 5-5, Fig. 1, to the position of 0., said tracks aregradually twisted to their position shown in Fig. 6. As the grippers 5and 6 travel with the conveyer chain adjacent the conveyer 3 and in thehorizontal position of Fig. 4 the cam tracks 12 and 13 with rollerbearing contact force the gripper fingers together with the sheet 1between them. To make harmless contact with the sheet I prefer to havethe gripper fingers faced with soft material such as sponge rubber.

As the sheet 1 feeds off the end of conveyer 3 it is held at spaced edgeportions by the gripper devices. I provide for gradually turning thesheet 1 from horizontal to vertical position after it leaves conveyer 3.This turning movement is carried on between the end of conveyer 3 andpoint e. The tracks 14 and 15 are gradually twisted and, as shown inFig. 2, the travel path is slanted upwardly (about half the width of thepaper sheet 1) until point e is reached. During this turning the faredge of the sheet is gradually turned downwardly as the supported end islifted upwardly. This action or path of the paper is clearly indicatedin Fig. 2. As each gripper device reaches point c it has turned to theposition shown in Fig. 6. And it keeps such vertical hanging positionbetween points 0 and d. While the sheet is being turned it is importantnot to have it wrinkled or strained. To help avoid any such action Iprefer to supply a fall board, indicated at 50 (Fig. 2) and the surfaceof this board is preferably curved transversely so as to follow thenatural curvature of the paper sheet as it twists from horizontal tovertical position. Such a board serves as a support against which thepaper slides gently as it twists and the board is a guide to keep thepaper smooth and avoid strains where the paper sheet is heavy.

Between points 0 and dl, Figs. 1 and 2, the paper sheet 1 travels whilehung in vertical position by the spaced gripper devices 5 and 6. In thisposition the sheet is exposed on both sides and is dried out to itsfinal condition as in loft drying. It is this final drying step that is,I be- I lieve, most important with respect to the final quality of thepaper. As the paper stock sets during the final drying stage, the dryingtemperature and all other drying conditions are far more important thanin the preliminary drying such as takes place on conveyers 2. I haveprovided for the vertical travel of the paper sheet from c to at so thatthe final drying step can be carried on under conditions of slow drying,at a temperature such as would be suitable for loft dried paper, and sothat the paper will not be duly strained. This vertical travel of theshe from c to d is a very long travel which the drawings cannot show.For example, it may long enough to go from one end to the other of a rylong mill room in which the end por ti of apparatus occupy aninsignificant part. Instead of being a straight travel it may be a basiand forth conveyer travel. My plan includes the idea of making thevertical travel ,or another sheet and repeat the cycle.

example, that if a single sheet of paper were going to be loft driedaccording to the old regular method, it would be in the loft dried roomfor its proper length of time if it were hung on a gripper device of myconveyer and carried the length of the vertical travel. This time ofcourse varies with the paper to be dried and other conditions, but thoseskilled in the art will appreciate that particular feature of myinvention that I want to emphasize-namely, that the vertical travelofthesheet in my apparatus is planned to give the results of loft driedpaper in a better manner as to paper support and paper handling, butotherwise as if the paper were loft dried.

During the long slow vertical travel of the sheet 1 between points 0 andd the paper is shrinking. To avoid shrinking strains I have provided themeans indicated in Fig. 8. At frequent intervals I provide the camtracks 12 and 13 in the vertical travel path of sheet 1, with portionsto successively release and againapply gripper fingers 5 and 6. Thus asthe paper shrinks and tends to set up a strain between the gripperdevices along the supported edge, such devices are successively releasedand reapplied by the cam tracks 12 and 13. When reapplied the papersheet 1 has moved slightly (due to the released shrinking strain) andeach gripper device takes hold at a slightly offset position.

When the sheet reaches point'd it is dried. As indicated in Fig. l, thegrippers beyond d cross over and carry the sheet down to a horizontalposition and lay it on wind-up conveyer 39. This cross over results inturning the sheet completely over in its travel from one end of theapparatus to the other. As it is desired to turn the sheet 1 fromhorizontal to vertical and back to horizontal travel, it is a help toturn the sheet completely, as this tends to hold the vertical positionof the sheet naturally at the cross over portion and relieves strain.

It will be clear from Figs. 1 and 2 that the travel-of the sheet frompoint d up the rising board 51 with the grippers to the horizontalposition for laying the sheet on conveyer 39 is the reverse action tothat already described at the feed end of the apparatus. There is a freemargin of the paper overlying conveyer 39 for the grippers to bereleased, and they are released by the reverse action to that whichcauses them to grip the paper on conveyer 3. The grippers then return ontheir back conveyer travel (indicated in Fig. 1) to again fasten on thecontinuous sheet In the return of the grippers on the conveyer it isdesirable, as shown. to turn them completely over as they approachconveyer 3, and this can be done between points e and f of Fig. l bysuitably twisting the guide tracks. The dried sheet is wound oif ofconveyer 39 to roll b by any usual wind-up means.

In Fig. 9 I have illustrated diagrammatically a modified means forturning the paper sheet from horizontal to vertical and back again. ifthe paper is fed off conveyer 2 under the angularly disposed guide roll61 (the hearing s EE'IES other end of the apparatus, as indicated, avertical travel between points 0 and d" is provided. In this arrangementroll 51 is horizontally arranged at a 45 angle to the line of travel;guide roll 62 is slanted with its axis at a 45 angle to a horizontalplane and at a 90 angle to the axis of roll 61. Rolls 63 and 64 aresimilarly arranged. This arrangement of turning a paper sheet is commonin printing presses and the like. Used in my apparatus it has theadvantage of avoiding the twisting and turning of the conveyen tracks,cam tracks and grippers to accommodate the desired horizontal andvertical position of the paper sheet. In the modification of Fig. 9 asimpler endless conveyer such as is shown in cross sectionin Fig. 6could be mounted above the sheet travel from points 0 to d and thegrippers 5 and 6 could grasp and release the paper all along such travelas indicated in Fig. 8,

and without the necessity of twisting the grippers about from horizontalto vertical and even completely around as in the case of the formindicated in the other figures.

The reason I have shown a more complicated form of apparatus than thatindicated in Fig. 8 is because there is some advantage in handling heavyand wide sheets of paper with a more gradual and gentler means ofturning the wet sheet about than that shown in Fig. 9. It is obviousthat I can readily combine the two ways of turning the sheet in the sameapparatus. In such a case I would prefer to turn the wet sheet tovertical position as described in connection with Fig. 1 and turn thedry sheet at the delivery end, as described in connection with Fig. 9.In this kind of an arrangement cam tracks 12 and 13 would release thegrippers from sheet 1 at point d" in Fig. l, and turning guide rolls 63and 64 would turn it to horizontal for wind-up conveyer 39 and roll b.

The conveyer chain 10 with grippers 5 and 6 will travel so slowly thatno fine machine work is necessary on the apparatus. I have not attemptedto show all the guide pulleys and driving means that will be necessaryin such a long and heavy mechanism. Those skilled in conveyer mechanismcan readily supply those ordinary things. i

Having described my invention what I claim 1. Apparatus forprogressively and continuously'drying a paper sheet comprising incombination, a conveyer to carry the sheet horizontally, a secondconveyer to carry the sheet vertically, and a third conveyer to againcarry the sheet horizontally, said conveyers being arranged in series,means forming part of the second conveyer to take hold of the sheetalong one edge while it is on the first conveyer and support it invertical hanging position as it falls off the first conveyer to becarried by the second conveyer, said second-conveyer having a longenough path to carry the sheet in vertical hanging position until itdries, said third conveyer being arranged to receive the sheet when dryand as the second conveyer releases it.

2. In apparatus for drying paper comprising in combination conveyermeans to carry the paper horizontally with one edge exposed for grippingmeans to take hold at said edge, means to turn the paper gradually fromhorizontal to vertical position, gripping means to fasten on said edgewhile the paper is in horizontal position and support the paper when itis'turned to vertical position, an endless conveyer to carry saidgripping means, means to turn the paper from its vertical to ahorizontal position, devices to operate said gripping means to fasten onthe paper and to release the paper respectively before it turns tocessive pairs of said grippers so that the paper may shrink withoutexcessive strain between the grippers as the conveyer carries the sheetthrough a drying path.

4. An automatic apparatus for handling a continuous web of paper fordrying it comprising in combination a drying room, a conveyer operablein a closed path to carry the paper through the drying room, saidconveyer having a series of spaced grippers to support the paper fromspaced portions along one edge and permit the web to hang with bothsides in otherwise free and fully exposed vertical position with its topedge directed along the line of the conveyer travel while travelingthrough the drying room, means to feed one edge of the web into positionfor said grippers to take hold successively, a gripper operating deviceto cause the grippers to thus take hold, a second gripper operatingdevice to cause the grippers to let go of the paper when it is dry andmeans to take and support the dried web when the grippers release it.

5. An apparatus for drying paper comprising a drying room suitable fordrying paper under the loft-dried method, an endless conveyer having along path in said drying room, said conveyer having releasable means tohold a eontinuous web of paper along one edge and with such edgedirected along the line of the conveyer travel so that it hangsvertically and well exposed for drying as it travels in said room, andmeans to operate a part of said releasable means to compensate forshrinkage during the drying of the paper, I

6. An apparatus for drying paper comprising a drying room suitable fordrying paper under the loft-dried method, an endless conveyer having along path' in said drying room, said conveyer having releasable means tohold a continuous web of paper along one edge and with .such edgedirected along the line of the conveyer veyer having releasable means tohold a continuous web of paper solely along one edge so that it hangsvertically and with both sides well exposed and out of contact with allparts of the apparatus except said edge holding means for drying as ittravels in said room, and mechanism associated with said conveyer tooperate the releasable means as the paper shrinks in the dryingoperation FRANK C. LADD.

